Flash lamp



June13, 1944. F. J. RIPPL ETAL 2,351,290

FLASH LAMP Filed April 8, 1942 lnvenfors: Francis J. RippL, ELmer B. lsaacifi/ Their A'f't'orney.

Patented June 13, 1944 UNITED STATES PATENT-OFFICE 2351.290

' Francis J. Bippl, Cleveland, and Elmer B. Isaac. Cleveland Heights, Ohio, aasignors to General Electric Company, a corporation of New York Application April 8, 1942, sci-n1 No. 43am 4 Claims. (01. 67-31) intensity. More particularly. our invention relates to combustible material for such flash lamps. The present application is a continuation-in-part of our copending applications Serial No. 322,520, filed March 6, 1940; Serial No. 353,650, filed August 22, 1940; and Serial No. 383,096, filed March 13, 1941.

Prior to the present invention, the combustible material generally employed in flash lamps consisted either of a quantity oi extremely thin metallic foil or a quantity of extremely fine metallic wire. The foil, generally of aluminum, was of the order of approximately 0.000015 to 0.000020 inch thickness. To obtain such extremely thin foil, the aluminum was first rolled into thin sheets and then beaten between suitable beating forms, in the manner known for the preparation of gold foils, until the desired thinness was obtained. Such a heating process is slow and costly, making the aluminum foil quite expensive. Likewise, the wire used heretofore and at the present time in flash lamps, and which generally consists of aluminum or magnesium or their alloys, must undergo an involved and expensive wire-drawing process in order to be drawn to the required size or fineness, generally 1.5 mils or less in diameter, for satisfactory flash lamp use. Thus, up to the present invention, there has been no relatively inexpensive combustible filling material for flash lamps. f

One object of our invention'is to provide a flash lamp having a loose filling of a relatively inexpensive combustible material.

Another object of our invention is to provide a flash lamp having a loose filling of combustible material comprising a light and fiuiiy mass of shredded metal foil the individual shreds of which are of substantially uniform cross-section.

Further objects and advantages of our invention will appear from the following description of a species thereof and from the accompanying drawing, in which:

Fig. 1 is an elevation of a flash lamp comprising our invention, Fig. 2 is a diagrammatic illustration showing the method of manufacturing the combustible flash lamp material comprising our invention and a suitable method of loading such material into the bulb of the flash lamp; and Fig. 3 shows cross-sectional views of several strands of the shredded foil as it appears when magnified 670 times.

Referring to the drawing, the flash lamp according to the invention comprises a sealed lighttransmitting bulb or envelope of suitable material, such'as glass. Mounted within the bulb is a small filament ii the ends of which are con nected to the inner tips of a pair of leading-in wires l2, I! which extend through a re-entrant stem i3 to a base it secured to the neck of the bulb. The inner tips of the leading-in wires l2.

l2, and at least a portion of the filament ii, are

coated with a layer of. a suitable fulminating substance It to thereby form the primer or i tion means for the lamp. The fulmin'ating material i5 is preferably of the type disclosed and claimed in copending United States patent application Serial No. 278,288-G. H. Meridith, filed June 9, 1939, and assigned to the assignee of the present application. The bulb is coated on its inner or outer surface, preferably on both surfaces, with a coating of a suitable light-transmitting varnish or lacquer to thereby minimize cracking of the bulb on charge flashing and to render the bulb substantially shatterproof.

The bulb i0 is filled with a quantity of readily combustible material It of the type comprising our invention, the said material being loosely arranged within and uniformly distributed throughout the bulb l0 so as to surround the ignition filament I i. The bulb i 0 is also filled with a combustion-supporting gas such as oxygen or an oxygen-containing gas, at a suitable pressure, for supporting the combustion of the combustible material 16. The pressure of this gaseous filling will vary, depending upon the type of gas employed, the size of the bulb, and the quantity and type of combustible material therein. For bulb sizes in commercial use at present, and with oxygen being used as the combustion-supporting gas and pure aluminum as the combustible material, the pressure of the gaseous filling may vary up to 600 mm. of mercuryor even close to one atmosphere. Preferably, however, the pressure of the oxygen is between about 450 to 600 mm. of mercury.

The combustible material It according to our invention comprises a quantity of shredded metal foil which is sliced or shredded from a thin metal sheet or strip I1 (Fig. 2) which has been previously rolled to the thinness (i. e., of the order of approximately 0.001 inch or less) which the finally out shreds are, to possess. The individual shreds or strands are cut to a width of the order of about .001 inch or less, and should have a cross-sectional area of the order of 1 /2 square mils or less. The shredded foil material is preferably made of aluminum, although other materials may be used such as magnesium or alloys of aluminum and/or magnesium. Where aluminum is used, the sheet i1 is preferably of the type known as full hard aluminum.

The shredded foil filling material 16 is produced by the method disclosed and claimed in our said copending applications Serial Nos. 353,650 and 383,096. The rolled sheet ll of aluminum is in the form of a continuous strip of uniform width, such as from six to twelve Lucheabut preferably about eight inches wide, which iswound manufacture. Rolled foils of full hard" aluminum one mil and below in thickness are comertheless it is insuificiently thin to be effectively edge 20, as to cut shreds'of foil ofa uniform width of the order of .001 inch wide or thereabouts. The strands of shredded foil made in this-manner are characterized by the presence of burrs of microscopic size extending longitudinally thereof- The minuteburrs are shown at It in Fig. 3. l The shredded foil material l6, after its manufacture, is then loaded into the bulb of a flash lamp byv any suitable procedure. Thus, a quantity of shredded foil sufficient to constitutethe filling for a single lamp may be gathered together and fiuifed out by a suitable small rodshaped tool, and the fiuiIed out mass of shredded foil then-stuffed into and distributed throughout the bulbby the said tool. Preferably, however, the shredded foil material I6 is pneumatically loaded into the flash lamp bulb in themanner described and claimed in copending United States application-Serial No. 374,372, Geiger et al., filed January 14, 1941 and assigned to the as signee of the present invention. As therein disclosed, the bulb 23 to be filled is placed over one the knife edge 20. The open end or neck 26 of the bulb is then connected to a source of vacuum, through the filling head 21 and tube 28 as shown, with the result that the suction in the feed tube 24 causes the individual shreds of metal foil, as they are cut, to be drawn through the suction nozzle 25 and feed tube 24. The shreds of metal foil are then discharged into the interior of the bulb 23 where, because of their curled, crinkled or rumpled condition and the restrictedair-outlet space between the bulb neck and the feed tube, the said metal foil shreds are trapped and gradually fill up the entire bulb to form a uniformly distributed tangled mass of shredded foil therein.

The shredded foi1 material It according to the invention is extremely light and flufly, and possesses very little, if any, elasticity. In fact, the

said material is so light that the air alone flufls it up, in which fiufied condition the shredded foil material will remain against all ordinary handling and shipping impacts but will tend to compact somewhat when the lamp bulb is subjected to excessive sharp impacts. The light and substantially inelastic shredded foil filling material according to the invention is thus quite different from wirefilling material such as disclosed in United States Patent No. 2,162,847Korver, issued June 20, 1939. With such wire material, it is necessary to introduce an internal strain in the-wire in order to impart inherent elasticity thereto. It is the inherent elasticity, then, of the wire itself which serves to maintain such wire filling ma terial in an expanded condition, the wire possessing elasticity to a'degree such that the wire fllling cannot be compacted even when the lamp bulb is subjected to excessive impacts.

ignitable when comparatively wide strips are used as the'filling materialfor flash lamps. However, by simply cutting such rolled aluminum foil of the order ofone mil thickness into shreds having a width of the order of one mil, a very inexpensive and satisfactory filamentary combustible material is obtained.

The rolled foil, :as.obtained commercially, is of substantially uniform thickness. Consequently, by cutting such uniform thickness foil into shreds of substantially uniform width, the individual shreds will be of uniform cross-section so that different flash lamps filled with such material will possess uniform flash characteristics.

Although, as stated above, the shredded foil material It comprising'our invention will retain its fluffed out condition under normal shocks or impacts, still, if desired, it may be positively secured in place within the bulb in the manner disclosed and claimed in copending United States application Serial No. 285,980-J. H. Oram, filed July 22, 1939 and assigned to the assignee of the present invention. As therein disclosed, the combustible materialis secured at a plurality of spaced points to the inner bulb wall by means of a lacquer coating on the inner surface of the bulb, those portions of the combustible material IS in contact with the inner coating being embedded therein to thereby provide a positive affixation of the material within the bulb.

While we prefer to use our shredded foil material I6 as the sole combustible filling material in flash lamps, nevertheless, it is entirely possible to combine it with other well-known types of combustible material, such as the conventional beaten foils or fine-drawn wires of aluminum or magnesium or their alloys, to thereby obtain any desired flash characteristics.

What we claim as new'and desire to secure by Letters Patent of the United States is:

1. In a flash lamp of the character described comprising a sealed light transmitting container, 9. combustible filling material consisting of a flufied out mass of fine metallic strands having burrs thereon serving to render said strands more easily ignitable.

2. In a flash lamp of the character described comprising a sealed light transmitting container, a combustible filling material consisting of a fiufied out mass of fine strands of aluminum having burrs thereon serving to render said strands more easily ignitable.

3. In a fiash lamp of the character described comprising a sealed lighttransmitting container, a combustible filling material consisting of a fiufied out mass of fine metallic strands having comprising a sealed light transmitting container, I

burrs thereon serving to render said strands more easily ignitable, the individual strands having a cross-section of the order of a square mil.

4. In a flash lamp of the character described a combustible filling material consisting of a fluifed out mass of fine-strands of aluminum having burrs thereon serving to render said strands more easily ignitable, the individual strands having a cross-section of the order of a square mil.

FRANCIS J. RIPPL. ELMER B. ISAAC. 

